Procedure for Conducting Polarized Electron Measurements with One Channeltron

The purpose of this procedure is to obtain measurements of the electron arrival rate at the channeltron as a function of the incident beam energy, with a variable direction of variation of the beam energy, to protect against drift effects.

1. The electron gun's beam energy $E_b$ was set to $(500\pm{}0.3)\,\mathrm{eV}$, with corresponding adjustments (table A.1) in the voltages on the polarimeter's front grid, thorium foil, and retarding grids.
2. The dwell time $\tau$ of the data acquisition apparatus (chapter 3) was set to $1\,\mathrm{s}$. The reasons for choosing this dwell time are discussed in section 5.5.
3. The electron gun's beam current $F$ was set to $(4\pm{}0.1)\,\mathrm{\mu{}A}$.
4. A series of electron arrival rate measurements was taken, according to the procedure in appendix A.4.
5. $\tau$ was set to $50\,\mathrm{ms}$. The reasons for choosing this dwell time are discussed in section 5.5.
6. Either an ascending or a descending order was chosen for incident beam energies $E_b$. If the procedure being described here had been performed previously, then the order chosen was opposite to that chosen in the preceding performance of the procedure. Otherwise, an order was chosen at random.
7. The electron gun beam energy, along with the voltages on the polarimeter's front grid, thorium foil, and retarding grids, was varied, in the chosen order, in $50\,\mathrm{eV}$ steps between $500\,\mathrm{eV}$ and $1\,\mathrm{keV}$ inclusive, with a random error of $300\,\mathrm{meV}$ in each beam energy.
8. At each of the beam energies, a series of electron arrival rate measurements was taken, according to the procedure in appendix A.3.